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Results for “Pattern Recognition, Physiological”

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At least 199 records · Page 11Linked to original sources
PubMed1990

Pattern-recognition by an artificial network derived from biologic neuronal systems.

A novel artificial neural network, derived from neurobiological observations, is described and examples of its performance are presented. This DYnamically STable Associative Learning (DYSTAL) network associatively learns both correlations and anticorrelations, and can be configured to classify or restore patterns with only a change in the number of output units. DYSTAL exhibits some particularly desirable properties: computational effort scales linearly with the number of connections, i.e., it is O(N) in complexity; performance of the network is stable with respect to network parameters over wide ranges of their values and over the size of the input field; storage of a very large number of patterns is possible; patterns need not be orthogonal; network connections are not restricted to multi-layer feed-forward or any other specific structure; and, for a known set of deterministic input patterns, the network weights can be computed, a priori, in closed form. The network has been associatively trained to perform the XOR function as well as other classification tasks. The network has also been trained to restore patterns obscured by binary or analog noise. Neither global nor local feedback connections are required during learning; hence the network is particularly suitable for hardware (VLSI) implementation.

Animals↗
PubMed2003

Searching for nodules: what features attract attention and influence detection?

RATIONALE AND OBJECTIVES: The goal of the study was to determine whether there are certain physical features of pulmonary nodules that attract visual attention and contribute to increased recognition and detection by observers. MATERIALS AND METHODS: A series of posteroanterior chest images with solitary pulmonary nodules were searched by six radiologists as their eye-position was recorded. The signal-to-noise ratio, size, conspicuity, location, and calcification status were measured for each nodule. Dwell parameters were correlated with nodule features and related to detection rates. RESULTS: Only nodule size (F = 5.08, P = .0254) and conspicuity (F = 4.625, P = .0329) influenced total dwell time on nodules, with larger, more conspicuous nodules receiving less visual attention than smaller, less conspicuous nodules. All nodule features examined influenced overall detection performance (P < .05) even though most did not influence visual search and attention. CONCLUSION: Individual nodule features do not attract attention as measured by "first hit" fixation data, but certain features do tend to hold attention once the nodule has been fixated. The combination of all features influences whether or not it is detected.

Attention↗
PubMed1980

Neocognitron: a self organizing neural network model for a mechanism of pattern recognition unaffected by shift in position.

A neural network model for a mechanism of visual pattern recognition is proposed in this paper. The network is self-organized by "learning without a teacher", and acquires an ability to recognize stimulus patterns based on the geometrical similarity (Gestalt) of their shapes without affected by their positions. This network is given a nickname "neocognitron". After completion of self-organization, the network has a structure similar to the hierarchy model of the visual nervous system proposed by Hubel and Wiesel. The network consists of an input layer (photoreceptor array) followed by a cascade connection of a number of modular structures, each of which is composed of two layers of cells connected in a cascade. The first layer of each module consists of "S-cells", which show characteristics similar to simple cells or lower order hypercomplex cells, and the second layer consists of "C-cells" similar to complex cells or higher order hypercomplex cells. The afferent synapses to each S-cell have plasticity and are modifiable. The network has an ability of unsupervised learning: We do not need any "teacher" during the process of self-organization, and it is only needed to present a set of stimulus patterns repeatedly to the input layer of the network. The network has been simulated on a digital computer. After repetitive presentation of a set of stimulus patterns, each stimulus pattern has become to elicit an output only from one of the C-cells of the last layer, and conversely, this C-cell has become selectively responsive only to that stimulus pattern. That is, none of the C-cells of the last layer responds to more than one stimulus pattern. The response of the C-cells of the last layer is not affected by the pattern's position at all. Neither is it affected by a small change in shape nor in size of the stimulus pattern.

Cognition↗
PubMed1992

Comparative effects of luminance and scatter on the pattern visual evoked potential and eye-hand reaction time.

We investigated the effect of reduced luminance and increased scatter on the pattern visual evoked potential and eye-hand reaction time evoked to a check size of 0.5 degrees in 10 normal subjects. Data analysis indicated that a reduction in luminance as well as an increase in scatter caused a statistically significant increase in the peak time of the pattern visual evoked potential P100 wave. The reaction time, however, was not significantly affected by the initial 0.9-log unit attenuation of the stimulus luminance or the 0.3 scatter filter. Further attenuation of luminance or increase of scatter also yielded statistically significant increases. Our results suggest that the reaction time is less affected by a reduction in luminance or an increase in scatter of a 0.5 degrees stimulus than the pattern visual evoked potential is and therefore represents a more reliable test to assess visual function, especially in the presence of medial opacities, which are known to reduce luminance and produce scatter.

Adolescent↗
PubMed1993

Topography and ocular dominance: a model exploring positive correlations.

The map from eye to brain in vertebrates is topographic, i.e., neighbouring points in the eye map to neighbouring points in the brain. In addition, when two eyes innervate the same target structure, the two sets of fibres segregate to form ocular dominance stripes. Experimental evidence from the frog and goldfish suggests that these two phenomena may be subserved by the same mechanisms. We present a computational model that addresses the formation of both topography and ocular dominance. The model is based on a form of competitive learning with subtractive enforcement of a weight normalization rule. Inputs to the model are distributed patterns of activity presented simultaneously in both eyes. An important aspect of this model is that ocular dominance segregation can occur when the two eyes are positively correlated, whereas previous models have tended to assume zero or negative correlations between the eyes. This allows investigation of the dependence of the pattern of stripes on the degree of correlation between the eyes: we find that increasing correlation leads to narrower stripes. Experiments are suggested to test this prediction.

Animals↗
PubMed1977

Temporal aspects of spatial vision in the cat.

Using behavioral techniques, contrast sensitivity for flickering and stationary gratings was measured in ordinary cats. Gratings of low spatial frequency were more easily detected by the cat when temporal modulation was present, but at high spatial frequencies temporal modulation reduced grating visibility. These psychophysical results are consistent with neurophysiological evidence for the existence of two classes of visual cells in the cat, which are distinguishable in terms of their spatio-temporal response properties.

Animals↗
PubMed1977

Spatial properties of binocular neurones in the human visual system.

The spatial properties of human binocular mechanisms were investigated using the technique of subthreshold summation. Isolation of binocular mechanisms was achieved by means of interocular stimulus presentation. The contrast detection threshold for a sinusoidal test grating viewed by one eye was found to be reduced by a subthreshold grating of the same spatial frequency and orientation seen by the other eye. The interaction between the gratings was approximately linear. Threshold increased as the spatial frequencies or orientations of test and subthreshold gratings were made increasingly different. Spatial stimulus specificities measured in this way were as great for interocular presentation as for simultaneous monocular presentation. The results suggest that human contrast sensitivity for gratings may depend upon binocularly-activated neurones similar to those found in cat and monkey visual cortex.

Humans↗
PubMed1980

Further consideration on pattern separability in a random neural net with inhibitory connections.

A two-layer random neural net with inhibitory connections composing of threshold elements has been regarded as a model of the cerebellar cortex. Many properties of pattern separation with the model have been disclosed through consideration on the degree of pattern separation. However, we have not shown yet that the degree of pattern separation is given by some different functions which are decided by the relation between the firing rates of input patterns. The present study is intended to reveal that the functions of the degree of pattern separation are synthesized with some different partial functions, and they are differently given on the relation between the firing rates of input patterns. Simultaneously, it is proved that the number of the functions also depend on the number of connections between two layers in the model. We also disclose the properties of the degree of pattern separation, and give some suggestions on the sizes of the firing rates of mossy fibers and granule cells under the knowledge about them.

Cerebellar Cortex↗
PubMed2000

Visual and acoustic communication in non-human animals: a comparison.

The visual and auditory systems are two major sensory modalities employed in communication. Although communication in these two sensory modalities can serve analogous functions and evolve in response to similar selection forces, the two systems also operate under different constraints imposed by the environment and the degree to which these sensory modalities are recruited for non-communication functions. Also, the research traditions in each tend to differ, with studies of mechanisms of acoustic communication tending to take a more reductionist tack often concentrating on single signal parameters, and studies of visual communication tending to be more concerned with multivariate signal arrays in natural environments and higher level processing of such signals. Each research tradition would benefit by being more expansive in its approach.

Acoustic Stimulation↗
PubMed1993

Sleep staging with movement-related signals.

Body movement related signals (i.e., activity due to postural changes and the ballistocardiac effort) were recorded from six normal volunteers using the static-charge-sensitive bed (SCSB). Visual sleep staging was performed on the basis of simultaneously recorded EEG, EMG and EOG signals. A statistical classification technique was used to determine if reliable sleep staging could be performed using only the SCSB signal. A classification rate of between 52% and 75% was obtained for sleep staging in the five conventional sleep stages and the awake state. These rates improved from 78% to 89% for classification between awake, REM and non-REM sleep and from 86% to 98% for awake versus asleep classification.

Adult↗